EX-10.8



 Exhibit 10.8 

PROTEOSTASIS THERAPEUTICS, INC. 

FORM OF INDEMNIFICATION AGREEMENT 

This Indemnification Agreement (“Agreement”) is made as of [●] by and between Proteostasis Therapeutics, Inc., a
Delaware corporation (the “Company”), and [●] (“Indemnitee”). 
 RECITALS 

WHEREAS, the Company desires to attract and retain the services of highly qualified individuals, such as Indemnitee, to serve the Company;

 WHEREAS, in order to induce Indemnitee to provide or continue to provide services to the Company, the Company wishes to provide for the
indemnification of, and advancement of expenses to, Indemnitee to the maximum extent permitted by law; 
 WHEREAS, the [Fourth] Amended and
Restated Certificate of Incorporation (the “Charter”) and the [Second] Amended and Restated Bylaws (the “Bylaws”) of the Company require indemnification of the officers and directors of the Company, and Indemnitee
may also be entitled to indemnification pursuant to the General Corporation Law of the State of Delaware (the “DGCL”); 

WHEREAS, the Charter, the Bylaws and the DGCL expressly provide that the indemnification provisions set forth therein are not exclusive, and
thereby contemplate that contracts may be entered into between the Company and members of the board of directors, officers and other persons with respect to indemnification; 

WHEREAS, the Board of Directors of the Company (the “Board”) has determined that the increased difficulty in attracting and
retaining highly qualified persons such as Indemnitee is detrimental to the best interests of the Company’s stockholders; 
 WHEREAS,
it is reasonable, prudent and necessary for the Company contractually to obligate itself to indemnify, and to advance expenses on behalf of, such persons to the fullest extent permitted by applicable law, regardless of any amendment or revocation of
the Charter or the Bylaws, so that they will serve or continue to serve the Company free from undue concern that they will not be so indemnified; [and] 

WHEREAS, this Agreement is a supplement to and in furtherance of the indemnification provided in the Charter, the Bylaws and any resolutions
adopted pursuant thereto, and shall not be deemed a substitute therefor, nor to diminish or abrogate any rights of Indemnitee thereunder[; and][.] 

  
 1 








 [Include for Director Agreement][WHEREAS, Indemnitee may have certain rights to
indemnification and/or insurance, including as provided by [Name of Fund/Sponsor], which are to be secondary to the primary obligation of the Company to indemnify Indemnitee as provided in this Agreement, with the
Company’s acknowledgment and agreement to the foregoing being a material condition to Indemnitee’s willingness to serve or continue to serve on the Board.] 

NOW, THEREFORE, in consideration of the premises and the covenants contained herein, the Company and Indemnitee do hereby covenant and agree
as follows: 
 Section 1. Services to the Company. Indemnitee agrees to serve as [a director][an officer] of the Company.
Indemnitee may at any time and for any reason resign from such position (subject to any other contractual obligation or any obligation imposed by law), in which event the Company shall have no obligation under this Agreement to continue Indemnitee
in such position. This Agreement shall not be deemed an employment contract between the Company (or any of its subsidiaries or any Enterprise) and Indemnitee. 

Section 2. Definitions. 

As used in this Agreement: 

(a) [Include in Director Agreement][”Change in Control” shall mean: 

(i) the date any “person,” as such term is used in Sections 13(d) and 14(d) of the Securities Exchange Act of 1934,
as amended (the “Act”) (other than the Company, any of its subsidiaries, or any trustee, fiduciary or other person or entity holding securities under any employee benefit plan or trust of the Company or any of its subsidiaries),
together with all “affiliates” and “associates” (as such terms are defined in Rule 12b-2 under the Act) of such person, becomes the “beneficial owner” (as such term is defined in Rule 13d-3 under the Act), directly or
indirectly, of securities of the Company representing 50 percent or more of the combined voting power of the Company’s then outstanding securities having the right to vote in an election of the Board (“Voting Securities”) (in
such case other than as a result of an acquisition of securities directly from the Company); or 
 (ii) the date a majority
of the members of the Board is replaced during any 12-month period by directors whose appointment or election is not endorsed by a majority of the members of the Board before the date of the appointment or election; or 

(iii) the date of consummation of (A) any consolidation or merger of the Company where the stockholders of the Company,
immediately prior to the consolidation or merger, would not, immediately after the consolidation or merger, beneficially own (as such term is defined in Rule 13d-3 under the Act), directly or indirectly, shares representing in the aggregate more
than 50 percent of the voting shares of the Company issuing cash or securities in the consolidation or merger (or of its ultimate parent corporation, if any), or (B) any sale or other transfer (in one transaction or a series of transactions
contemplated or arranged by any party as a single plan) of all or substantially all of the assets of the Company. 

  
 2 








 Notwithstanding the foregoing, a “Change in Control” will not be deemed to have
occurred for purposes of the foregoing clause (i) solely as the result of an acquisition of securities by the Company which, by reducing the number of shares of Voting Securities outstanding, increases the proportionate number of Voting
Securities beneficially owned by any person to 50 percent or more of the combined voting power of all of the then outstanding Voting Securities; provided, however, that if any person referred to in this sentence will thereafter become the beneficial
owner of any additional shares of Voting Securities (other than pursuant to a stock split, stock dividend, or similar transaction or as a result of an acquisition of securities directly from the Company) and immediately thereafter beneficially owns
50 percent or more of the combined voting power of all of the then outstanding Voting Securities, then a “Change in Control” will be deemed to have occurred for purposes of the foregoing clause (i).] 

(b) “Corporate Status” describes the status of a person as a current or former [director][officer] of the Company or current
or former director, manager, partner, officer, employee, agent or trustee of any other Enterprise which such person is or was serving at the request of the Company. 

(c) “Enforcement Expenses” shall include all reasonable attorneys’ fees, court costs, transcript costs, fees of experts,
travel expenses, duplicating costs, printing and binding costs, telephone charges, postage, delivery service fees, and all other out-of-pocket disbursements or expenses of the types customarily incurred in connection with an action to enforce
indemnification or advancement rights, or an appeal from such action. Expenses, however, shall not include fees, salaries, wages or benefits owed to Indemnitee. 

(d) “Enterprise” shall mean any corporation (other than the Company), partnership, joint venture, trust, employee benefit
plan, limited liability company, or other legal entity of which Indemnitee is or was serving at the request of the Company as a director, manager, partner, officer, employee, agent or trustee. 

(e) “Expenses” shall include all reasonable attorneys’ fees, court costs, transcript costs, fees of experts, travel
expenses, duplicating costs, printing and binding costs, telephone charges, postage, delivery service fees, and all other out-of-pocket disbursements or expenses of the types customarily incurred in connection with prosecuting, defending, preparing
to prosecute or defend, investigating, being or preparing to be a witness in, or otherwise participating in, a Proceeding or an appeal resulting from a Proceeding. Expenses, however, shall not include amounts paid in settlement by Indemnitee, the
amount of judgments or fines against Indemnitee or fees, salaries, wages or benefits owed to Indemnitee. 
 (f) “Independent
Counsel” means a law firm, or a partner (or, if applicable, member or shareholder) of such a law firm, that is experienced in matters of Delaware corporation law and neither presently is, nor in the past five (5) years has been,
retained to represent: (i) the Company, any subsidiary of the Company, any Enterprise or Indemnitee in any matter material to any such party; or (ii) any other party to the Proceeding giving rise to a claim for indemnification hereunder.
Notwithstanding the foregoing, the term “Independent Counsel” shall not include any person who, under the applicable standards of professional conduct then prevailing, would have a conflict of interest in representing either the
Company or 

  
 3 








 
Indemnitee in an action to determine Indemnitee’s rights under this Agreement. The Company agrees to pay the reasonable fees and expenses of the Independent Counsel referred to above and to
fully indemnify such counsel against any and all expenses, claims, liabilities and damages arising out of or relating to this Agreement or its engagement pursuant hereto. 

(g) The term “Proceeding” shall include any threatened, pending or completed action, suit, arbitration, alternate dispute
resolution mechanism, investigation, inquiry, administrative hearing or any other actual, threatened or completed proceeding, whether brought in the right of the Company or otherwise and whether of a civil, criminal, administrative, regulatory or
investigative nature, and whether formal or informal, in which Indemnitee was, is or will be involved as a party or otherwise by reason of the fact that Indemnitee is or was a [a director][an officer] of the Company or is or was serving at the
request of the Company as a director, manager, partner, officer, employee, agent or trustee of any Enterprise or by reason of any action taken by Indemnitee or of any action taken on his or her part while acting as a [a director][an officer] of the
Company or while serving at the request of the Company as a director, manager, partner, officer, employee, agent or trustee of any Enterprise, in each case whether or not serving in such capacity at the time any liability or expense is incurred for
which indemnification, reimbursement or advancement of expenses can be provided under this Agreement; provided, however, that the term “Proceeding” shall not include any action, suit or arbitration, or part thereof,
initiated by Indemnitee to enforce Indemnitee’s rights under this Agreement as provided for in Section 12(a) of this Agreement. 

Section 3. Indemnity in Third-Party Proceedings. The Company shall indemnify Indemnitee to the extent set forth in
this Section 3 if Indemnitee is, or is threatened to be made, a party to or a participant in any Proceeding, other than a Proceeding by or in the right of the Company to procure a judgment in its favor. Pursuant to this Section 3,
Indemnitee shall be indemnified against all Expenses, judgments, fines, penalties, excise taxes, and amounts paid in settlement actually and reasonably incurred by Indemnitee or on his or her behalf in connection with such Proceeding or any claim,
issue or matter therein, if Indemnitee acted in good faith and in a manner he or she reasonably believed to be in or not opposed to the best interests of the Company and, in the case of a criminal proceeding, had no reasonable cause to believe that
his or her conduct was unlawful.  
 Section 4. Indemnity in Proceedings by or in the Right of the Company. The
Company shall indemnify Indemnitee to the extent set forth in this Section 4 if Indemnitee is, or is threatened to be made, a party to or a participant in any Proceeding by or in the right of the Company to procure a judgment in its favor.
Pursuant to this Section 4, Indemnitee shall be indemnified against all Expenses actually and reasonably incurred by Indemnitee or on his or her behalf in connection with such Proceeding or any claim, issue or matter therein, if Indemnitee
acted in good faith and in a manner he or she reasonably believed to be in or not opposed to the best interests of the Company. No indemnification for Expenses shall be made under this Section 4 in respect of any claim, issue or matter as to
which Indemnitee shall have been finally adjudged by a court to be liable to the Company, unless and only to the extent that the Delaware Court of Chancery (the “Delaware Court”) shall determine upon application that, despite the
adjudication of liability but in view of all the circumstances of the case, Indemnitee is fairly and reasonably entitled to indemnification for such expenses as the Delaware Court shall deem proper. 

  
 4 








 Section 5. Indemnification for Expenses of a Party Who is Wholly or Partly
Successful. Notwithstanding any other provisions of this Agreement and except as provided in Section 7, to the extent that Indemnitee is a party to or a participant in any Proceeding and is successful in such Proceeding or in defense of any
claim, issue or matter therein, the Company shall indemnify Indemnitee against all Expenses actually and reasonably incurred by him or her in connection therewith. If Indemnitee is not wholly successful in such Proceeding but is successful as to one
or more but less than all claims, issues or matters in such Proceeding, the Company shall indemnify Indemnitee against all Expenses actually and reasonably incurred by Indemnitee or on his or her behalf in connection with each successfully resolved
claim, issue or matter. For purposes of this Section and without limitation, the termination of any claim, issue or matter in such a Proceeding by dismissal, with or without prejudice, shall be deemed to be a successful result as to such claim,
issue or matter. 
 Section 6. Reimbursement for Expenses of a Witness or in Response to a Subpoena. Notwithstanding any other
provision of this Agreement, to the extent that Indemnitee, by reason of his or her Corporate Status, (i) is a witness in any Proceeding to which Indemnitee is not a party and is not threatened to be made a party or (ii) receives a
subpoena with respect to any Proceeding to which Indemnitee is not a party and is not threatened to be made a party, the Company shall reimburse Indemnitee for all Expenses actually and reasonably incurred by him or her or on his or her behalf in
connection therewith. 
 Section 7. Exclusions. Notwithstanding any provision in this Agreement to the contrary,
the Company shall not be obligated under this Agreement:  
 (a) to indemnify for amounts otherwise indemnifiable hereunder
(or for which advancement is provided hereunder) if and to the extent that Indemnitee has otherwise actually received such amounts under any insurance policy, contract, agreement or otherwise[Include in Director Agreement][; provided
that the foregoing shall not affect the rights of Indemnitee or the Secondary Indemnitors as set forth in Section 13(c)]; 
 (b) to
indemnify for an accounting of profits made from the purchase and sale (or sale and purchase) by Indemnitee of securities of the Company within the meaning of Section 16(b) of the [Securities Exchange] Act [of 1934, as amended,] or similar
provisions of state statutory law or common law; 
 [Include in Officer Agreement][(c) to indemnify for any reimbursement of, or
payment to, the Company by Indemnitee of any bonus or other incentive-based or equity-based compensation or of any profits realized by Indemnitee from the sale of securities of the Company pursuant to Section 304 of SOX or any formal policy of
the Company adopted by the Board (or a committee thereof), or any other remuneration paid to Indemnitee if it shall be determined by a final judgment or other final adjudication that such remuneration was in violation of law;] 

  
 5 








 (d) to indemnify with respect to any Proceeding, or part thereof, brought by Indemnitee against
the Company, any legal entity which it controls, any director or officer thereof or any third party, unless (i) the Board has consented to the initiation of such Proceeding or part thereof and (ii) the Company provides the indemnification,
in its sole discretion, pursuant to the powers vested in the Company under applicable law; provided, however, that this Section 7(d) shall not apply to (A) counterclaims or affirmative defenses asserted by Indemnitee in an
action brought against Indemnitee or (B) any action brought by Indemnitee for indemnification or advancement from the Company under this Agreement or under any directors’ and officers’ liability insurance policies maintained by the
Company in the suit for which indemnification or advancement is being sought as described in Section 12; or 
 (e) to provide any
indemnification or advancement of expenses that is prohibited by applicable law (as such law exists at the time payment would otherwise be required pursuant to this Agreement). 

Section 8. Advancement of Expenses. Subject to Section 9(b), the Company shall advance, to the extent not prohibited by law,
the Expenses incurred by Indemnitee in connection with any Proceeding, and such advancement shall be made within thirty (30) days after the receipt by the Company of a statement or statements requesting such advances (which shall include
invoices received by Indemnitee in connection with such Expenses but, in the case of invoices in connection with legal services, any references to legal work performed or to expenditures made that would cause Indemnitee to waive any privilege
accorded by applicable law need not be included with the invoice) from time to time, whether prior to or after final disposition of any Proceeding. Advances shall be unsecured and interest free. Advances shall be made without regard to
Indemnitee’s ability to repay the expenses and without regard to Indemnitee’s ultimate entitlement to indemnification under the other provisions of this Agreement. Indemnitee shall qualify for advances upon the execution and delivery to
the Company of this Agreement which shall constitute an undertaking providing that Indemnitee undertakes to the fullest extent required by law to repay the advance if and to the extent that it is ultimately determined by a court of competent
jurisdiction in a final judgment, not subject to appeal, that Indemnitee is not entitled to be indemnified by the Company. The right to advances under this paragraph shall in all events continue until final disposition of any Proceeding, including
any appeal therein. Nothing in this Section 8 shall limit Indemnitee’s right to advancement pursuant to Section 12(e) of this Agreement. 

Section 9. Procedure for Notification and Defense of Claim. 

(a) To obtain indemnification under this Agreement, Indemnitee shall submit to the Company a written request therefor specifying the basis for
the claim, the amounts for which Indemnitee is seeking payment under this Agreement, and all documentation related thereto as reasonably requested by the Company. 

(b) In the event that the Company shall be obligated hereunder to provide indemnification for or make any advancement of Expenses with respect
to any Proceeding, the Company shall be entitled to assume the defense of such Proceeding, or any claim, issue or matter therein, with counsel approved by Indemnitee (which approval shall not be unreasonably withheld or delayed) upon the delivery to
Indemnitee of written notice of the Company’s election to do so. After delivery of such notice, approval of such counsel by Indemnitee and the retention of such counsel by the Company, the Company will not be liable to Indemnitee under this


  
 6 








 
Agreement for any fees or expenses of separate counsel subsequently employed by or on behalf of Indemnitee with respect to the same Proceeding; provided that (i) Indemnitee shall have
the right to employ separate counsel in any such Proceeding at Indemnitee’s expense and (ii) if (A) the employment of separate counsel by Indemnitee has been previously authorized by the Company, (B) Indemnitee shall have
reasonably concluded that there may be a conflict of interest between the Company and Indemnitee in the conduct of such defense, or (C) the Company shall not continue to retain such counsel to defend such Proceeding, then the reasonable fees
and expenses actually and reasonably incurred by Indemnitee with respect to his or her separate counsel shall be Expenses hereunder. 
 (c)
In the event that the Company does not assume the defense in a Proceeding pursuant to paragraph (b) above, then the Company will be entitled to participate in the Proceeding at its own expense. 

(d) The Company shall not be liable to indemnify Indemnitee under this Agreement for any amounts paid in settlement of any Proceeding effected
without its prior written consent (which consent shall not be unreasonably withheld or delayed). The Company shall not, without the prior written consent of Indemnitee (which consent shall not be unreasonably withheld or delayed), enter into any
settlement which (i) includes an admission of fault of Indemnitee, any non-monetary remedy imposed on Indemnitee or any monetary damages for which Indemnitee is not wholly and actually indemnified hereunder or (ii) with respect to any
Proceeding with respect to which Indemnitee may be or is made a party or may be otherwise entitled to seek indemnification hereunder, does not include the full release of Indemnitee from all liability in respect of such Proceeding. 

Section 10. Procedure Upon Application for Indemnification. 

(a) Upon written request by Indemnitee for indemnification pursuant to Section 9(a), a determination, if such determination is required
by applicable law, with respect to Indemnitee’s entitlement to indemnification hereunder shall be made in the specific case by one of the following methods: [Include in Director Agreement][(x) if a Change in Control shall have occurred,
by Independent Counsel in a written opinion to the Board; or (y) if a Change in Control shall not have occurred:] (i) by a majority vote of the disinterested directors, even though less than a quorum; (ii) by a committee of
disinterested directors designated by a majority vote of the disinterested directors, even though less than a quorum; (iii) if there are no disinterested directors or if the disinterested directors so direct, by Independent Counsel in a written
opinion to the Board[Include in Director Agreement][; or (iv) if so directed by the Board, by the stockholders of the Company]. For purposes hereof, disinterested directors are those members of the Board who are not parties to the
action, suit or proceeding in respect of which indemnification is sought. In the case that such determination is made by Independent Counsel, a copy of Independent Counsel’s written opinion shall be delivered to Indemnitee and, if it is so
determined that Indemnitee is entitled to indemnification, payment to Indemnitee shall be made within thirty (30) days after such determination. Indemnitee shall cooperate with the Independent Counsel or the Company, as applicable, in making
such determination with respect to Indemnitee’s entitlement to indemnification, including providing to such counsel or the Company, upon reasonable advance request, any documentation or information which is not


  
 7 








 
privileged or otherwise protected from disclosure and which is reasonably available to Indemnitee and reasonably necessary to such determination. Any [Include in Officer
Agreement][reasonable] out-of-pocket costs or expenses (including reasonable attorneys’ fees and disbursements) actually and reasonably incurred by Indemnitee in so cooperating with the Independent Counsel or the Company shall be borne by
the Company (irrespective of the determination as to Indemnitee’s entitlement to indemnification) and the Company hereby indemnifies and agrees to hold Indemnitee harmless therefrom. 

(b) If the determination of entitlement to indemnification is to be made by Independent Counsel pursuant to Section 10(a), the
Independent Counsel shall be selected by the Board [Include in Director Agreement][if a Change in Control shall not have occurred or, if a Change in Control shall have occurred, by Indemnitee]. Indemnitee [Include in Director
Agreement][or the Company, as the case may be,] may, within ten (10) days after written notice of such selection, deliver to the Company [Include in Director Agreement][or Indemnitee, as the case may be,] a written objection to such
selection; provided, however, that such objection may be asserted only on the ground that the Independent Counsel so selected does not meet the requirements of “Independent Counsel” as defined in Section 2 of this
Agreement, and the objection shall set forth with particularity the factual basis of such assertion. Absent a proper and timely objection, the person so selected shall act as Independent Counsel. If such written objection is so made and
substantiated, the Independent Counsel so selected may not serve as Independent Counsel unless and until such objection is withdrawn or the Delaware Court has determined that such objection is without merit. If, within twenty (20) days after
the later of (i) submission by Indemnitee of a written request for indemnification pursuant to Section 9(a), and (ii) the final disposition of the Proceeding, including any appeal therein, no Independent Counsel shall have been
selected without objection, either Indemnitee or the Company may petition the Delaware Court for resolution of any objection which shall have been made by Indemnitee or the Company to the selection of Independent Counsel and/or for the appointment
as Independent Counsel of a person selected by the court or by such other person as the court shall designate. The person with respect to whom all objections are so resolved or the person so appointed shall act as Independent Counsel under
Section 10(a) hereof. Upon the due commencement of any judicial proceeding or arbitration pursuant to Section 12(a) of this Agreement, Independent Counsel shall be discharged and relieved of any further responsibility in such capacity
(subject to the applicable standards of professional conduct then prevailing). 
 Section 11. Presumptions and Effect of Certain
Proceedings. 
 (a) To the extent permitted by applicable law, in making a determination with respect to entitlement to indemnification
hereunder, it shall be presumed that Indemnitee is entitled to indemnification under this Agreement if Indemnitee has submitted a request for indemnification in accordance with Section 9(a) of this Agreement, and the Company shall have the
burden of proof to overcome that presumption in connection with the making of any determination contrary to that presumption. [Include in Director Agreement][Neither (i) the failure of the Company or of Independent Counsel to have made a
determination prior to the commencement of any action pursuant to this Agreement that indemnification is proper in the circumstances because Indemnitee has met the applicable standard of conduct, nor (ii) an actual determination by the Company
or by Independent Counsel that Indemnitee has not met such applicable standard of conduct, shall be a defense to the action or create a presumption that Indemnitee has not met the applicable standard of conduct.] 

  
 8 








 (b) The termination of any Proceeding or of any claim, issue or matter therein, by judgment,
order, settlement or conviction, or upon a plea of guilty, nolo contendere or its equivalent, shall not (except as otherwise expressly provided in this Agreement) of itself adversely affect the right of Indemnitee to indemnification or create
a presumption that Indemnitee did not act in good faith and in a manner which he or she reasonably believed to be in or not opposed to the best interests of the Company or, with respect to any criminal Proceeding, that Indemnitee had reasonable
cause to believe that his or her conduct was unlawful. 
 (c) The knowledge and/or actions, or failure to act, of any director, manager,
partner, officer, employee, agent or trustee of the Company, any subsidiary of the Company, or any Enterprise shall not be imputed to Indemnitee for purposes of determining the right to indemnification under this Agreement. 

Section 12. Remedies of Indemnitee. 

(a) Subject to Section 12(f), in the event that (i) a determination is made pursuant to Section 10 of this Agreement that
Indemnitee is not entitled to indemnification under this Agreement, (ii) advancement of Expenses is not timely made pursuant to Section 8 of this Agreement, (iii) no determination of entitlement to indemnification shall have been made
pursuant to Section 10(a) of this Agreement within sixty (60) days after receipt by the Company of the request for indemnification for which a determination is to be made other than by Independent Counsel, (iv) payment of
indemnification or reimbursement of expenses is not made pursuant to Section 5 or 6 or the last sentence of Section 10(a) of this Agreement within thirty (30) days after receipt by the Company of a written request therefor (which
shall include any invoices received by Indemnitee but, in the case of invoices in connection with legal services, any references to legal work performed or to expenditures made that would cause Indemnitee to waive any privilege accorded by
applicable law need not be included with the invoice) or (v) payment of indemnification pursuant to Section 3 or 4 of this Agreement is not made within thirty (30) days after a determination has been made that Indemnitee is entitled
to indemnification, Indemnitee shall be entitled to an adjudication by the Delaware Court of his or her entitlement to such indemnification or advancement. Alternatively, Indemnitee, at his or her option, may seek an award in arbitration to be
conducted by a single arbitrator pursuant to the Commercial Arbitration Rules of the American Arbitration Association. Indemnitee shall commence such proceeding seeking an adjudication or an award in arbitration within 180 days following the date on
which Indemnitee first has the right to commence such proceeding pursuant to this Section 12(a); provided, however, that the foregoing time limitation shall not apply in respect of a proceeding brought by Indemnitee to enforce his
or her rights under Section 5 of this Agreement. The Company shall not oppose Indemnitee’s right to seek any such adjudication or award in arbitration. 

  
 9 








 (b) In the event that a determination shall have been made pursuant to Section 10(a) of this
Agreement that Indemnitee is not entitled to indemnification, any judicial proceeding or arbitration commenced pursuant to this Section 12 shall be conducted in all respects as a de novo trial, or arbitration, on the merits and Indemnitee shall
not be prejudiced by reason of that adverse determination. In any judicial proceeding or arbitration commenced pursuant to this Section 12, the Company shall have the burden of proving Indemnitee is not entitled to indemnification or
advancement, as the case may be. 
 (c) If a determination shall have been made pursuant to Section 10(a) of this Agreement that
Indemnitee is entitled to indemnification, the Company shall be bound by such determination in any judicial proceeding or arbitration commenced pursuant to this Section 12, absent (i) a misstatement by Indemnitee of a material fact, or an
omission of a material fact necessary to make Indemnitee’s statement not materially misleading, in connection with the request for indemnification, or (ii) a prohibition of such indemnification under applicable law. 

(d) The Company shall be precluded from asserting in any judicial proceeding or arbitration commenced pursuant to this Section 12 that
the procedures and presumptions of this Agreement are not valid, binding and enforceable and shall stipulate in any such court or before any such arbitrator that the Company is bound by all the provisions of this Agreement. 

(e) The Company shall indemnify Indemnitee to the fullest extent permitted by law against any and all Enforcement Expenses and, if requested
by Indemnitee, shall (within thirty (30) days after receipt by the Company of a written request therefor) advance, to the extent not prohibited by law, such Enforcement Expenses to Indemnitee, which are incurred by Indemnitee in connection with
any action brought by Indemnitee for indemnification or advancement from the Company under this Agreement or under any directors’ and officers’ liability insurance policies maintained by the Company in the suit for which indemnification or
advancement is being sought. Such written request for advancement shall include invoices received by Indemnitee in connection with such Enforcement Expenses but, in the case of invoices in connection with legal services, any references to legal work
performed or to expenditures made that would cause Indemnitee to waive any privilege accorded by applicable law need not be included with the invoice. 

(f) Notwithstanding anything in this Agreement to the contrary, no determination as to entitlement to indemnification under this Agreement
shall be required to be made prior to the final disposition of the Proceeding, including any appeal therein. 
 Section 13.
Non-exclusivity; Survival of Rights; Insurance; [Include in Director Agreement][Primacy of Indemnification;] Subrogation. 

(a) The rights of indemnification and to receive advancement as provided by this Agreement shall not be deemed exclusive of any other rights
to which Indemnitee may at any time be entitled under applicable law, the Charter, the Bylaws, any agreement, a vote of stockholders or a resolution of directors, or otherwise. No amendment, alteration or repeal of this Agreement or of any provision
hereof shall limit or restrict any right of Indemnitee under this Agreement in respect of any action taken or omitted by such Indemnitee in his or her Corporate Status prior to such amendment, alteration or repeal. To the extent that a change in
Delaware law, whether by statute or judicial decision, permits greater indemnification or advancement than would be afforded currently under the Charter, the Bylaws and this Agreement, it is the intent of the parties hereto that Indemnitee shall
enjoy by this Agreement the 

  
 10 








 
greater benefits so afforded by such change. No right or remedy herein conferred is intended to be exclusive of any other right or remedy, and every other right and remedy shall be cumulative and
in addition to every other right and remedy given hereunder or now or hereafter existing at law or in equity or otherwise. The assertion or employment of any right or remedy hereunder, or otherwise, shall not prevent the concurrent assertion or
employment of any other right or remedy. 
 (b) To the extent that the Company maintains an insurance policy or policies providing liability
insurance for directors, managers, partners, officers, employees, agents or trustees of the Company or of any other Enterprise, Indemnitee shall be covered by such policy or policies in accordance with its or their terms to the maximum extent of the
coverage available for any such director, manager, partner, officer, employee, agent or trustee under such policy or policies. If, at the time of the receipt of a notice of a claim pursuant to the terms hereof, the Company has director and officer
liability insurance in effect, the Company shall give prompt notice of the commencement of such proceeding to the insurers in accordance with the procedures set forth in the respective policies. [Include in Director Agreement][The Company
shall thereafter take all necessary or desirable action to cause such insurers to pay, on behalf of Indemnitee, all amounts payable as a result of such proceeding in accordance with the terms of such policies. 

(c) The Company hereby acknowledges that Indemnitee may have certain rights to indemnification, advancement of expenses and/or insurance
provided by third parties (collectively, the “Secondary Indemnitors”), including as provided by [Name of Fund/Sponsor] and certain of [its][their] affiliates. The Company hereby agrees (i) that it is the
indemnitor of first resort (i.e., its obligations to Indemnitee are primary and any obligation of the Secondary Indemnitors to advance expenses or to provide indemnification for the same expenses or liabilities incurred by Indemnitee are
secondary), (ii) that it shall be required to advance the full amount of expenses incurred by Indemnitee and shall be liable for the full amount of all Expenses, judgments, penalties, fines and amounts paid in settlement to the extent legally
permitted and as required by the terms of this Agreement and the Charter and/or Bylaws (or any other agreement between the Company and Indemnitee), without regard to any rights Indemnitee may have against the Secondary Indemnitors, and
(iii) that it irrevocably waives, relinquishes and releases the Secondary Indemnitors from any and all claims against the Secondary Indemnitors for contribution, subrogation or any other recovery of any kind in respect thereof. The Company
further agrees that no advancement or payment by the Secondary Indemnitors on behalf of Indemnitee with respect to any claim for which Indemnitee has sought indemnification from the Company shall affect the foregoing and the Secondary Indemnitors
shall have a right of contribution and/or be subrogated to the extent of such advancement or payment to all of the rights of recovery of Indemnitee against the Company. The Company and Indemnitee agree that the Secondary Indemnitors are express
third party beneficiaries of the terms of this Section 13(c). At the request of Indemnitee, the Company shall acknowledge in writing its obligations under this Section 13(c) to any Secondary Indemnitors.] 

(d) [Include in Director Agreement][Except as provided in paragraph (c) above,] [I/i]n the event of any payment under this
Agreement, the Company shall be subrogated to the extent of such payment to all of the rights of recovery of Indemnitee (other than against the Secondary Indemnitors), who shall execute all papers required and take all action necessary to secure
such rights, including execution of such documents as are necessary to enable the Company to bring suit to enforce such rights. 

  
 11 








 (e) [Include in Director Agreement][Except as provided in paragraph (c) above,]
[T/t]he Company’s obligation to provide indemnification or advancement hereunder to Indemnitee who is or was serving at the request of the Company as a director, manager, partner, officer, employee, agent or trustee of any other Enterprise
shall be reduced by any amount Indemnitee has actually received as indemnification or advancement from such other Enterprise. 

Section 14. Duration of Agreement. This Agreement shall continue until and terminate upon the later of: (a) ten
(10) years after the date that Indemnitee shall have ceased to serve as a [a director][an officer] of the Company or (b) one (1) year after the final termination of any Proceeding, including any appeal, then pending in respect of
which Indemnitee is granted rights of indemnification or advancement hereunder and of any proceeding commenced by Indemnitee pursuant to Section 12 of this Agreement relating thereto. This Agreement shall be binding upon the Company and its
successors and assigns and shall inure to the benefit of Indemnitee and his or her heirs, executors and administrators. The Company shall require and cause any successor (whether direct or indirect by purchase, merger, consolidation or otherwise) to
all, substantially all or a substantial part, of the business and/or assets of the Company, by written agreement in form and substance satisfactory to Indemnitee, expressly to assume and agree to perform this Agreement in the same manner and to the
same extent that the Company would be required to perform if no such succession had taken place. 
 Section 15. Severability. If
any provision or provisions of this Agreement shall be held to be invalid, illegal or unenforceable for any reason whatsoever: (a) the validity, legality and enforceability of the remaining provisions of this Agreement (including, without
limitation, each portion of any section of this Agreement containing any such provision held to be invalid, illegal or unenforceable, that is not itself invalid, illegal or unenforceable) shall not in any way be affected or impaired thereby and
shall remain enforceable to the fullest extent permitted by law; (b) such provision or provisions shall be deemed reformed to the extent necessary to conform to applicable law and to give the maximum effect to the intent of the parties hereto;
and (c) to the fullest extent possible, the provisions of this Agreement (including, without limitation, each portion of any section of this Agreement containing any such provision held to be invalid, illegal or unenforceable, that is not
itself invalid, illegal or unenforceable) shall be construed so as to give effect to the intent manifested thereby. 
 Section 16.
Enforcement. 
 (a) The Company expressly confirms and agrees that it has entered into this Agreement and assumed the obligations
imposed on it hereby in order to induce Indemnitee to serve or continue to serve as a [a director][an officer] of the Company, and the Company acknowledges that Indemnitee is relying upon this Agreement in serving as a [a director][an officer] of
the Company. 

  
 12 








 (b) This Agreement constitutes the entire agreement between the parties hereto with respect to
the subject matter hereof and supersedes all prior agreements and understandings, oral, written and implied, between the parties hereto with respect to the subject matter hereof; provided, however, that this Agreement is a supplement
to and in furtherance of the Charter, the Bylaws and applicable law, and shall not be deemed a substitute therefor, nor to diminish or abrogate any rights of Indemnitee thereunder. 

Section 17. Modification and Waiver. No supplement, modification or amendment, or waiver of any provision, of this Agreement shall
be binding unless executed in writing by the parties thereto. No waiver of any of the provisions of this Agreement shall be deemed or shall constitute a waiver of any other provisions of this Agreement nor shall any waiver constitute a continuing
waiver. No supplement, modification or amendment of this Agreement or of any provision hereof shall limit or restrict any right of Indemnitee under this Agreement in respect of any action taken or omitted by such Indemnitee prior to such supplement,
modification or amendment. 
 Section 18. Notice by Indemnitee. Indemnitee agrees promptly to notify the Company in writing upon
being served with any summons, citation, subpoena, complaint, indictment, information or other document relating to any Proceeding or matter which may be subject to indemnification, reimbursement or advancement as provided hereunder. The failure of
Indemnitee to so notify the Company shall not relieve the Company of any obligation which it may have to Indemnitee under this Agreement or otherwise. 

Section 19. Notices. All notices, requests, demands and other communications under this Agreement shall be in writing and shall be
deemed to have been duly given if (i) delivered by hand and receipted for by the party to whom said notice or other communication shall have been directed, (ii) mailed by certified or registered mail with postage prepaid, on the third
business day after the date on which it is so mailed, (iii) mailed by reputable overnight courier and receipted for by the party to whom said notice or other communication shall have been directed or (iv) sent by facsimile transmission,
with receipt of oral confirmation that such transmission has been received: 
  

	 	(a)	If to Indemnitee, at such address as Indemnitee shall provide to the Company. 

  

	 	(b)	If to the Company to: 

 Proteostasis Therapeutics, Inc. 

200 Technology Square 
 Suite
402 
 Cambridge, MA 02139 

Attention: Chief Executive Officer 
 or to any
other address as may have been furnished to Indemnitee by the Company. 
 Section 20. Contribution. To the fullest extent
permissible under applicable law, if the indemnification provided for in this Agreement is unavailable to Indemnitee for any reason whatsoever, the Company, in lieu of indemnifying Indemnitee, shall contribute to the amount incurred by Indemnitee,
whether for judgments, fines, penalties, excise taxes, amounts paid or to be paid in settlement and/or for Expenses, in connection with any Proceeding in such proportion as is deemed fair and reasonable in light of all of the circumstances in order
to reflect (i) the 

  
 13 








 
relative benefits received by the Company and Indemnitee in connection with the event(s) and/or transaction(s) giving rise to such Proceeding; and/or (ii) the relative fault of the Company
(and its directors, officers, employees and agents) and Indemnitee in connection with such event(s) and/or transactions. 
 Section 21.
Internal Revenue Code Section 409A. The Company intends for this Agreement to comply with the Indemnification exception under Section 1.409A-1(b)(10) of the regulations promulgated under the Internal Revenue Code of 1986, as amended
(the “Code”), which provides that indemnification of, or the purchase of an insurance policy providing for payments of, all or part of the expenses incurred or damages paid or payable by Indemnitee with respect to a bona fide claim
against Indemnitee or the Company do not provide for a deferral of compensation, subject to Section 409A of the Code, where such claim is based on actions or failures to act by Indemnitee in his or her capacity as a service provider of the
Company. The parties intend that this Agreement be interpreted and construed with such intent. 
 Section 22. Applicable Law and
Consent to Jurisdiction. This Agreement and the legal relations among the parties shall be governed by, and construed and enforced in accordance with, the laws of the State of Delaware, without regard to its conflict of laws rules. Except with
respect to any arbitration commenced by Indemnitee pursuant to Section 12(a) of this Agreement, the Company and Indemnitee hereby irrevocably and unconditionally (i) agree that any action or proceeding arising out of or in connection with
this Agreement shall be brought only in the Delaware Court, and not in any other state or federal court in the United States of America or any court in any other country, (ii) consent to submit to the exclusive jurisdiction of the Delaware
Court for purposes of any action or proceeding arising out of or in connection with this Agreement, (iii) consent to service of process at the address set forth in Section 19 of this Agreement with the same legal force and validity as if
served upon such party personally within the State of Delaware, (iv) waive any objection to the laying of venue of any such action or proceeding in the Delaware Court, and (v) waive, and agree not to plead or to make, any claim that any
such action or proceeding brought in the Delaware Court has been brought in an improper or inconvenient forum. 
 Section 23.
Headings. The headings of the paragraphs of this Agreement are inserted for convenience only and shall not be deemed to constitute part of this Agreement or to affect the construction thereof. 

Section 24. Identical Counterparts. This Agreement may be executed in one or more counterparts, each of which shall for all
purposes be deemed to be an original but all of which together shall constitute one and the same Agreement. Only one such counterpart signed by the party against whom enforceability is sought needs to be produced to evidence the existence of this
Agreement. 
 [Remainder of Page Intentionally Left Blank] 

  
 14 








 IN WITNESS WHEREOF, the parties have caused this Agreement to be signed as of the day and year
first above written. 
  

							
	COMPANY:	 		 	PROTEOSTASIS THERAPEUTICS, INC.
				
		 		 	By:	 	 
		 		 	Name:
		 		 	Title:

 INDEMNITEE: 
  

							
				
		 		 	 	 	 
		 		 	[Name of Indemnitee]